Data tiering is a hierarchical storage management technique wherein data is moved between high-cost/high-performance storage to low-cost/low performance storage based on the data usage pattern. Dynamic Storage Tiering (DST) is a concept of grouping storage devices into tiers based on their performance characteristics and relocating data dynamically across the devices to leverage their specific capabilities. A DST system performs this relocation while data remains online and accessible.
For performance management, data that has a high activity or load level may be relocated to high performing storage tiers. Alternately, data with a low activity level may be relocated to lower performing storage tiers in order to provide increased capacity in high-performance storage tiers. Such a data movement may be achieved by specialized software that is application/file system aware and resides on host systems (e.g. IBM's Tivoli Storage Manager, Veritas Enterprise Vault etc.) and data movement here is usually at a file level.